<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="../css/bootstrap.css">
    <script src="../js/bootstrap.js"></script>
    <style>
        .level-1,
        .level-3 {
            border: 1px solid red;
            height: 100px;
        }

        .level-2 {
            border: 1px solid blue;
        }
    </style>
</head>

<body>
    <div id="app" class="container">
        <div class="row item1">
            <div class="col-md-9 level-1">
                level1:9列
                <div class="row">
                    <div class="col-md-6 level-2">level2 6列</div>
                    <div class="col-md-6 level-2">level2 6列</div>
                </div>
                <div class="row">
                    <div class="col-md-6 level-2">level2 6列</div>
                    <div class="col-md-6 level-2">level2 6列</div>
                </div>
                <div class="row">
                    <div class="col-md-1 level-2"> 1列</div>
                    <div class="col-md-4 level-2">level2 3列</div>
                    <div class="col-md-2 level-2">level2 3列</div>
                    <div class="col-md-5 level-2">level2 3列</div>
                </div>
            </div>
            <div class="col-md-3 level-3">3列</div>
        </div>
    </div>
</body>

</html>